<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>后台首页</title>
    <style>
        body{
            margin: 0;
            padding: 0;
        }
        .out{
            border: 1px solid rgba(0,0,0,0.3);
            border-radius: 10px;
        }
        .out .header{
            border-bottom: 1px solid rgba(0,0,0,0.3);
            border-radius: 5px;
            height: 50px;
        }
        .out .show_msg{
            border: 1px solid red;
            margin: 5px;
            height: 500px;
            border-radius: 10px;
        }
    </style>
</head>
<body>
    <div class="out">
        <div class="header"></div>
        <div class="show_msg"></div>
    </div>
</body>
</html>